| ObjectivesThe first is to compare electrochemiluminescence immunoassay(ECLIA)with liquid chromatography-tandem mass spectrometry(LC-MS/MS)for the determination of serum 25hydroxyvitamin D[25(OH)D]in diabetic patients.The correlation and concordance between the results of 25-HydroxyvitaminD[25(OH)D]and liquid chromatography-tandem mass spectrometry(LC-MS/MS)were investigated to determine the optimal diagnostic cut-off point for the diagnosis of vitamin D deficiency in diabetic patients by ECLIA.The second is to compare the correlation between serum 25(OH)D levels and various metabolic indicators and neurological parameters using the gold standard LC-MS/MS method,and to further investigate the clinical application of vitamin D in diabetic peripheral neuropathy(DPN).MethodsIn this study,222 diabetic patients who met the criteria and voluntarily participated in the study were enrolled.Firstly,the serum samples of the patients were tested for 25(OH)D concentration by LC-MS/MS and ECLIA method respectively,and the correlation and consistency between the values of the two methods were analysed using LC-MS/MS as the gold standard.The best diagnostic cut-off point for the ECLIA method was determined using the receiver operating characteristic curve(ROC).Secondly,general data,anthropometric data,laboratory tests and neurological parameters were collected from all patients,and the differences in 25(OH)D levels detected by LC-MS/MS were compared in the total population,in different DPN groups and in different age groups,and correlated with each index.Research findings:1.The ECLIA method showed a positive bias(26.402%)compared to the LC-MS/MS method,and the correlation coefficient between the twors=0.491(P<0.0001),which can be obtained by regression equation as YLC-MS/MS=-3.486+0.987XECLIA extrapolated from each other.The area under the ROC curve for the ECLIA method was 0.78 when the LC-MS/MS test value of<20ng/mL was used as the diagnostic criterion for vitamin D deficiency and 0.69 when the LC-MS/MS test value of<10ng/mL was used as the diagnostic criterion for severe vitamin D deficiency.The kappa coefficients were 0.41 and 0.15 respectively when assessing the consistency of the ECLIA method with the gold standard for the diagnosis of vitamin D deficiency and severe deficiency using a uniform test threshold.3.The optimal cut point for the diagnosis of vitamin D deficiency by the ECLIA method was 21.36 ng/mL and the optimal cut point for the diagnosis of severe vitamin D deficiency was 16.68 ng/mL by ROC curve analysis.4.The results of the LC-MS/MS method showed that patients in the DPN group had higher levels of total 25(OH)D and 25(OH)D3 than those in the NDPN group,and the difference was statistically significant(P<0.05).5.In the total population,total 25(OH)D levels detected by LC-MS/MS were negatively correlated with FPG.TC,TG,Hcy and NSE,and 25(OH)D3 levels were negatively correlated with FPG.TG and NSE.6.In the NDPN group,total 25(OH)D levels and 25(OH)D3 levels detected by LC-MS/MS were negatively correlated with FPG and TG and positively correlated with right tibial nerve conduction velocity(P<0.05);in the non-painful DPN group,total 25(OH)D levels detected by LC-MS/MS were negatively correlated with TG and positively correlated with right median nerve conduction velocity(P<0.05).In the non-painful DPN group,total 25(OH)D level and 25(OH)D3 level by LC-MS/MS were negatively correlated with TG and negatively correlated with right median nerve conduction velocity(P<0.05);in the painful DPN group,total 25(OH)D level and 25(OH)D3 level by LC-MS/MS were positively correlated with HbAlc,left IWL and left CNBD(P<0.05).8.In the youth group,total 25(OH)D levels by LC-MS/MS did not correlate with any indexes,and 25(OH)D3 levels negatively correlated with NSE and TC(P<0.05);in the middleaged group,total 25(OH)D levels by LC-MS/MS and 25(OH)D3 levels negatively correlated with FPG and TG(P<0.05);in the elderly group,total 25(OH)D levels by LC-MS/MS negatively correlated with TG and Hcy,and 25(OH)D levels negatively correlated with TG and TG(P<0.05).0.05);in the elderly group,total 25(OH)D levels detected by LC-MS/MS were negatively correlated with TG and Hcy,and 25(OH)D3 levels were negatively correlated with TG(P<0.05).9.Multiple linear regression analysis found that in patients with painful DPN,IWL was positively correlated with 25(OH)D levels by LC-MS/MS and negatively correlated with BMI.Research findings:1.The ECLIA method for the detection of serum 25(OH)D levels in diabetic patients correlates well with the LC-MS/MS method and is of clinical diagnostic value.However,the overall value of the ECLIA method is high,and different diagnostic cutpoints need to be used.This study recommends that when applying the ECLIA method to assess the degree of vitamin D deficiency in diabetic patients,21.36 ng/mL should be used as the diagnostic cutpoint for vitamin D deficiency,and 16.68 ng/mL should be used as the diagnostic cutpoint for severe vitamin D deficiency.2.The relationship between vitamin D and DPN varies depending on the type of DPN.When tested by the gold standard LC-MS/MS method,25(OH)D levels are more closely associated with small nerve fibre damage in patients with painful DPN than with large nerve fibre damage,and higher 25(OH)D levels are associated with less nerve damage in small fibres. |
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